Precipitation Hardening High Entropy Alloy and Method of Manufacturing the Same

ABSTRACT

High-entropy alloy, particularly a precipitation hardening high entropy alloy, is provided as a component material used in electromagnetic, chemical, shipbuilding, mechanical, and other applications, a component material used in extreme environments requiring high strength and good corrosion resistance, and the like.

BACKGROUND 1. Field

The present disclosure relates to a metal alloy, in detail, ahigh-entropy alloy, used as a component material in a device havingelectromagnetic, chemical, shipbuilding, mechanical, and otherapplications, a component material used in extreme environmentsrequiring high strength and good corrosion resistance, and the like.

2. Description of Related Art

Due to technological breakthroughs in industrial technology,conventional metals and alloys according to the related art havelimitations in satisfying performance required for various applications.To satisfy requirements for enhanced properties and multifunctionality,a new type of material referred to as a high-entropy alloy has recentlybeen proposed and developed.

A high-entropy alloy typically refers to a multi-component single phasealloy formed by the reduction of total free energy of the solid solutionsingle phase due to a significant increase in configuration entropy ofthe multi-component system, prohibiting the formation of intermetalliccompounds. In other words, a high-entropy alloy refers not to anintermetallic compound or an amorphous alloy, but to a stable singlephase multi-component alloy.

A high-entropy alloy is disclosed in Non-Patent Document 1 (MaterialsScience and Engineering A, Vol. 0.375-377, 2004, page 213-218). InNon-Patent Document 1, a multi-element alloy, Fe₂₀Cr₂₀Mn₂₀Ni₂₀Co₂₀,expected to be formed as an amorphous alloy or complex intermetalliccompound, is unexpectedly formed as a crystalline face-centered cubic(FCC) solid solution, thereby raising interest. High-entropy alloys haveunusual characteristics in which a single phase is formed, even whenalloying elements are mixed in similar amounts in a quartenary, quinary,or higher system, as compared to the case in which an alloy according tothe related art is formed by adding additional alloying elements to amain alloying element present in an amount of 60 weight % to 90 weight%, the unusual characteristics being found in an alloy system in which adegree of configuration entropy is high due to mixing.

A high-entropy alloy is an alloy system containing four or more types ofmetal having an atomic concentration between 5 at % and 35 at %, and inwhich all alloying elements, having been added, act as a main element.If a high configurational entropy is induced due to a similar atomicfraction of elements in an alloy, a solid solution, which is stable athigh temperature, is formed instead of intermetallic compounds.

As prior art related to high-entropy alloys, there are provided PatentDocument 1 (U.S. Laid-Open Patent No. US 2013/0108502 A1) and PatentDocument 2 (U.S. Laid-Open Patent No. 2009/0074604 A1). In PatentDocument 1, disclosed is a high-entropy alloy having high hardness andelasticity (an elastic modulus), and formed as a single phase solidsolution having a face-centered cubic and/or body-centered cubicstructure. In addition, the high-entropy alloy is provided as an alloysystem containing five or more elements, in which each element such asvanadium (V), niobium (Nb), tantalum (Ta), molybdenum (Mo), titanium(Ti), or the like is included with a deviation of ±15 atomic % or less,as various metals, and in which all elements, having been added, act asa main element. However, in Patent Document 1, different types ofrelatively expensive and heavy alloying elements are added, so there maybe a difficulty in a manufacturing process due to a wide difference ofmelting points among the alloying elements having been added.

Meanwhile, in Patent Document 2, disclosed is a high-entropy alloyhaving a high hardness, manufactured in a powder metallurgy processusing a ceramic powders (representatively, a tungsten carbide) andmulti-component high-entropy alloy powders. The high-entropy alloy isformed as a single phase solid solution having a face-centered cubicand/or body-centered cubic structure, and thus having excellentmechanical properties. However, in Patent Document 2, since a hightemperature process is required when a ceramic material is used tomanufacture an alloy, a problem in which limitations on manufacturingare present may occur.

In recent years, while breaking a method of manufacturing a high-entropyalloy using a solid solution single-phase, there has been growinginterest in a high-entropy alloy in which a single phase and a secondphase are mixed. In addition, research into strengthening mechanismssuch as solid solution strengthening, precipitation strengthening,composite materials, and the like, has been extensively undertaken. InPatent Document 3 (CN Laid-Open Patent No. 104694808 A), a technique isprovided in which a Ni₃(Ti, Al) intermetallic compound is dispersed in ahigh-entropy alloy matrix, so excellent mechanical properties areimplemented.

SUMMARY OF THE INVENTION

An aspect of the present disclosure provides a high-entropy alloy, indetail, a high-entropy alloy with excellent strength and ductility byforming a nanoscale and/or sub-micron precipitate by adding alloyingelements with no or limited solubility, nitride or carbide formingelements, or the like, while a matrix maintains high configurationalentropy due to formation of the solid solution phase of various majoralloying elements comprising the matrix; and a method of manufacturingthe same.

According to an aspect of the present disclosure, a precipitationhardening high-entropy alloy includes:

four or more selected from the group consisting of more than 5 wt % to35 wt % or less of iron (Fe), more than 5 wt % to 35 wt % or less ofchromium (Cr), more than 5 wt % to 35 wt % or less of nickel (Ni), morethan 5 wt % to 35 wt % or less of manganese (Mn), more than 5 wt % to 35wt % or less of cobalt (Co), more than 5 wt % to 35 wt % or less ofcopper (Cu);

one or more of 1) and 2):

1) one or more of interstitial atoms such as; 0.01 wt % to 1.5 wt % ofcarbon (C), 0.01 wt % to 1.5 wt % of nitrogen (N), and 0.01 wt % to 1.5wt % of boron (B),

2) one or more of substitutional atoms such as; 0.01 wt % to 5 wt % oftitanium (Ti), 0.01 wt % to 5 wt % of zirconium (Zr), 0.01 wt % to 5 wt% of hafnium (Hf), 0.01 wt % to 5 wt % of molybdenum (Mo), 0.01 wt % to5 wt % of tungsten (W), 0.01 wt % to 5 wt % of niobium (Nb), 0.01 wt %to 5 wt % of vanadium (V), 0.01 wt % to 5 wt % of tantalum (Ta), 0.01 wt% to 5 wt % of silver (Ag), 0.01 wt % to 5 wt % of silicon (Si), 0.01 wt% to 5 wt % of copper (Cu), and 0.01 wt % to 5 wt % of germanium (Ge);and

inevitable residual impurities,

wherein the high-entropy alloy is provided with a high entropy matrix inwhich precipitates are dispersed.

According to another aspect of the present disclosure, a method ofmanufacturing a precipitation hardening high-entropy alloy includes:preparing a metal including

four or more selected from the group consisting of more than 5 wt % to35 wt % or less of Fe, more than 5 wt % to 35 wt % or less of Cr, morethan 5 wt % to 35 wt % or less of Ni, more than 5 wt % to 35 wt % orless of Mn, more than 5 wt % to 35 wt % or less of Co, and more than 5wt % to 35 wt % or less of Cu, and

one or more of 1) and 2):

1) one or more of interstitial atoms such as; 0.01 wt % to 1.5 wt % ofcarbon (C), 0.01 wt % to 1.5 wt % of nitrogen (N), and 0.01 wt % to 1.5wt % of boron (B),

2) one or more of substitutional atoms such as; 0.01 wt % to 5 wt % ofTi, 0.01 wt % to 3 wt % of Zr, 0.01 wt % to 5 wt % of Hf, 0.01 wt % to 5wt % of Mo, 0.01 wt % to 5 wt % of W, 0.01 wt % to 5 wt % of Nb, 0.01 wt% to 5 wt % of V, 0.01 wt % to 5 wt % of Ta, 0.01 wt % to 5 wt % of Ag,0.01 wt % to 5 wt % of Si, 0.01 wt % to 5 wt % of Cu, and 0.01 wt % to 5wt % of Ge, and

inevitable residual impurities; manufacturing an alloy by melting theconstituent metals, having been prepared; homogenization heat treatingthe alloy, having been manufactured, at a temperature within a range of600° C. to 1200° C.; cooling the alloy after the homogenization heattreating; and secondary heat treating the alloy by maintaining the alloyat a temperature within a range of 350° C. to 1000° C. for a certainperiod of time after cooling and cooling the alloy.

BRIEF DESCRIPTION OF DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawings will be provided by the Office upon request and paymentof the necessary fee.

The above and other aspects, features, and advantages of the presentdisclosure will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIGS. 1A and 1B are schematic diagrams illustrating a microstructure ofa high-entropy alloy according to the present disclosure, FIG. 1Aillustrates a microstructure before secondary heat treatment, and FIG.1B illustrates a microstructure after secondary heat treatment;

FIGS. 2A and 2B are electron micrographs illustrating a microstructureaccording to Inventive Example 7 of Example of the present disclosure,FIG. 2A illustrates in color a microstructure before secondary heattreatment, and FIG. 2B illustrates a microstructure after secondary heattreatment;

FIG. 3 is an image of a microstructure according to Inventive Example 2of Example of the present disclosure; and

FIG. 4 is a flowchart illustrating an example of a manufacturing methodaccording to the present disclosure.

DETAILED DESCRIPTION

The inventors of the present disclosure conducted research into a methodfor improving mechanical/physical properties such as strength,ductility, and the like of a high-entropy alloy. As a result, unlike thecase in which various alloying elements form a single-phase solidsolution, it can be confirmed that when nanoscale and/or sub-micronprecipitates are formed in a high-entropy alloy matrix, high ductilityand high strength characteristics can be secured at the same time. Indetail, a non-metallic alloying element, such as carbon (C), nitrogen(N), boron (B), or the like is added to a high-entropy alloy over asolubility limit to precipitate a carbonitride, a nitride, a boride, orthe like. Alternatively, a metallic element, such as titanium (Ti),zirconium (Zr), molybdenum (Mo), tungsten (W), silver (Ag), silicon(Si), copper (Cu), niobium (Nb), hafnium (Hf), vanadium (V), tantalum(Ta), germanium (Ge), or the like is added thereto to form precipitates.Thus, it can be confirmed that a high-entropy alloy with excellentstrength and ductility is provided, leading to the present disclosure.

Hereinafter, a high-entropy alloy according to the present disclosurewill be described in detail. First, a composition of a high-entropyalloy according to the present disclosure will be described in detail.

A high-entropy alloy according to the present disclosure includes

four or more selected from the group consisting of more than 5 wt % to35 wt % or less of iron (Fe), more than 5 wt % to 35 wt % or less ofchromium (Cr), more than 5 wt % to 35 wt % or less of Nickel (Ni), morethan 5 wt % to 35 wt % or less of manganese (Mn), more than 5 wt % to 35wt % or less of cobalt (Co), and more than 5 wt % to 35 wt % or less ofcopper (Cu),

one or more of 1) and 2):

1) one or more of interstitial atoms such as; 0.01 wt % to 1.5 wt % ofC, 0.01 wt % to 1.5 wt % of N, and 0.01 at % to 1.5 wt % of B

2) one or more of substitutional atoms such as; 0.01 wt % to 5 wt % ofTi, 0.01 wt % to 3 wt % of Zr, 0.01 wt % to 5 wt % of Hf, 0.01 wt % to 5wt % of Mo, 0.01 wt % to 5 wt % of W, 0.01 wt % to 5 wt % of Nb, 0.01 wt% to 5 wt % of V, 0.01 wt % to 5 wt % of Ta, 0.01 wt % to 5 wt % of Ag,0.01 wt % to 5 wt % of Si, 0.01 wt % to 5 wt % of Cu, and 0.01 wt % to 5wt % of Ge, and inevitable residual impurities.

Each of Fe, Cr, Ni, Mn, Co, and Cu, an element forming a high-entropyalloy matrix, is a fourth period transition element, and the differencein the atomic radius is small, thereby favoring the formation of a solidsolution, or the like. Each of Mn and Ni is an element promotingformation of a face-centered cubic (FCC) solid solution, Co promotesrefinement of a structure, Cr improves corrosion resistance, and Fe isan element promoting formation of a face-centered cubic (FCC) structureat intermediate temperatures and improves the strength. Here, thecontent of the elements is more than 5% to 35% or less, for the reasonto induce the increase of configurational entropy as much as possible ina uniform mixture, while not being outside of a range of entropy, forformation of a solid solution.

Meanwhile, C, B, and N are combined with Ti, Zr, Mo, W, Nb, V, Ta, Mn,Cr, or the like, in a high-entropy alloy to form a carbide, a nitride, aboride, or the like, and are precipitated in a matrix of a high-entropyalloy matrix, so the matrix may be strengthened and work hardenabilitymay be improved. Here, the content of each of C, N, and B is 0.01 wt %to 1.5 wt %. If the content of the element is insignificant, such as anamount of less than 0.01 wt %, precipitation hardenability may beinsignificant. If the content of the element exceeds 1.5 wt %, workhardenability may be reduced, so brittleness may occur.

In the case of Ti, Zr, Mo, W, Ag, Si, Cu, Nb, Hf, V, Ta, and Ge, adifference in the atomic radius from Fe, Cr, Ni, Mn, Co, and Cu, whichare main elements forming a matrix of a high-entropy alloy, is large,and a difference in the valency therefrom is also large. Thus, assolubility in a matrix of a high-entropy alloy is small, precipitationis favored, so the matrix may be strengthened by precipitationhardening. Thereamong, in the case in which Ti, Zr, Mo, W, Nb, V, Ta, orthe like is added with C, N, B, or the like, at the same time, acarbide, a nitride, or a boride may also be formed, so the matrix may bestrengthened. In the case in which one thereamong is added alone,elemental precipitates or intermetallic compounds are formed, so thematrix may be strengthened. Here, the content of each of Ti, Zr, Mo, W,Ag, Si, Cu, Hf, Nb, V, Ta, and Ge is 0.01 wt % to 5 wt %. If the contentthereof is less than 0.01 wt %, precipitation hardening effect isinsignificant. If the content thereof exceeds 5 wt %, the volumefraction and the size of precipitates exceed the limits, so workhardenability may be reduced and brittleness may be caused.

In the case of Ag, Si, Cu, Ge, and Hf, a difference in an atomic radiusfrom that of Fe, Cr, Ni, Mn, Co, and Cu, which are main elements forminga matrix of a high-entropy alloy, is large, and a difference in avalency, or the like therefrom is also large. Thus, solubility in ahigh-entropy alloy matrix is low, precipitation occurs, so a matrix maybe strengthened. Here, the content of each of Ag, Si, Cu, Ge, and Hf is0.01 wt % to 5 wt %. If the content thereof is lower than 0.01 wt %, anamount of a precipitation is insignificant. If the content thereofexceeds 5 wt %, the volume fraction and the size of precipitates exceedthe limits, so work hardenability may be reduced and brittleness may becaused.

Hereinafter, a microstructure of a high-entropy alloy according to thepresent disclosure will be described in detail. FIGS. 1A and 1B areschematic diagrams illustrating a microstructure of a high-entropyalloy. FIG. 1A illustrates a schematic microstructure (with coarsesecond phase particles) in which some elements, not dissolved butseparated from the matrix, are segregated as coarse particles in thematrix or at grain boundaries, before secondary heat treatment, in aprocess in which a high-entropy alloy according to the presentdisclosure is manufactured. FIG. 1B illustrates a schematicmicrostructure of precipitation hardened high-entropy alloy according tothe present disclosure in which a precipitate is uniformly dispersedthroughout a matrix, as the form illustrated in FIG. 1A processed bysecondary heat treatment.

The precipitate may be carbides, nitrides, borides, or the like, as Ti,Zr, Mo, W, Nb, V, Ta, or the like is combined with C, N, or B,interstitial alloying elements. Alternatively, in the case in which oneor more substitutional elements are added, without adding C, N, or B,the precipitates may be of the type that include one or more of Ti, Zr,Mo, W, Nb, V, Ta, Hf, Ag, Si, Cu, or Ge, and intermetallic compoundsthereof. In a precipitate hardened high-entropy alloy according to thepresent disclosure, nanoscale and sub-micron precipitates describedabove are precipitated in the matrix with high configurational entropy,so that excellent strength and ductility may be secured.

The precipitates in a high entropy alloy matrix block dislocationmovement or prevent annihilation of dislocations, so the density ofdislocation is increased, thereby enhancing the work hardening rate andstrength. It is preferable that the size of the precipitate has adiameter (or a length) of 0.5 nm to 50 nm and the spacing betweenprecipitates is 1 nm to 500 nm.

Hereinafter, a method of manufacturing a precipitation hardeninghigh-entropy alloy according to the present disclosure will be describedin detail. FIG. 4 illustrates a schematic sequence of a manufacturingmethod according to the present disclosure. Hereinafter, themanufacturing method according to the present disclosure will bedescribed with reference to FIG. 4.

To manufacture a high-entropy alloy according to the present disclosure,constituent materials are prepared, including four or more selected fromthe group consisting of more than 5 wt % to 35 wt % or less of Fe, morethan 5 wt % to 35 wt % or less of Cr, more than 5 wt % to 35 wt % orless of Ni, more than 5 wt % to 35 wt % or less of Mn, more than 5 wt %to 35 wt % or less of Co, and more than 5 wt % to 35 wt % or less of Cu,

1) one or more of 0.01 wt % to 1.5 wt % of C, 0.01 wt % to 1.5 wt % ofN, and 0.01 at % to 1.5 wt % of B,

2) one or more of 0.01 wt % to 5 wt % of Ti, 0.01 wt % to 3 wt % of Zr,0.01 wt % to 5 wt % of Hf, 0.01 wt % to 5 wt % of Mo, 0.01 wt % to 5 wt% of W, 0.01 wt % to 5 wt % of Nb, 0.01 wt % to 5 wt % of V, 0.01 wt %to 5 wt % of Ta, 0.01 wt % to 5 wt % of Ag, 0.01 wt % to 5 wt % of Si,0.01 wt % to 5 wt % of Cu, and 0.01 wt % to 5 wt % of Ge, and inevitableresidual impurities. Thereafter, melting, homogenization heat treatment,cooling, deformation processing and solution treatment if necessary, andsecondary heat treatment are performed to manufacture the precipitationhardening high-entropy alloy.

The melting is provided to allow the metal, having been manufactured, tobe alloyed, a method thereof is not particularly limited, and a methodcommonly performed in a technical field of the present disclosure isused. For example, the alloy is manufactured through casting, arcmelting, powder metallurgy, or the like.

Next, the alloy, having been manufactured, is homogenization heattreated. In a high-entropy alloy, various elements are mixed, sohomogenization heat treating is performed to induce sufficientdiffusion. It is preferable to perform the homogenization heat treatingat a temperature within a range of 600° C. to 1200° C. for 1 hour to 48hours.

After the homogenization heat treating, cooling is performed. A methodof the cooling is not particularly limited, and a method, such as watercooling, oil cooling, air cooling, or the like, may be performed.Through the homogenization and cooling, some microstructuralinhomogeniety are removed.

In order to develop a microstructure in which nanoscale and sub-micronprecipitates are present in a matrix, a single-phase solid solution, byforming the precipitate in the matrix after the cooling, secondary heattreatment is performed. The secondary heat treatment includes thesolution treatment and aging treatment. The solution treatment isperformed to allow an alloy to dissolve coarse second phase particlesand form the microstructure with no or minimal second phase particlesabove a solubility limit temperature (typically >700° C.) and then iscooled. In this case, the cooling may be performed in a method such aswater cooling, oil cooling, air cooling, furnace cooling, or the like.

The aging treatment is performed to allow an alloy to induceprecipitation of nanoscale and sub-micron second phase particles below asolubility limit temperature (typically <800° C.) by making somesupersaturated alloying elements in a thermodynamically unstable ormetastable state and then is cooled and nanoscale and sub-micron secondphase particles are uniformly precipitated in a matrix. The alloy ismaintained at a temperature within a range of 300° C. to 800° C. for 0.5hour to 72 hours, and then is cooled. In this case, the cooling may beperformed in a method such as water cooling, oil cooling, air cooling,furnace cooling, or the like, as described above.

Hereinafter, Examples according to the present disclosure will bedescribed in detail. The Examples are for the purpose of understandingthe present disclosure and are not intended to limit the presentdisclosure.

Example

First, as illustrated in Table 1, a high-entropy alloy according toComparative Examples 1 through 3 and Inventive Examples 1 through 13 ismanufactured.

Pieces of constituent pure metals weighted to attain a composition (wt%) of Table 1 were prepared, and the mixed pieces were arc melted in avacuum atmosphere to manufacture an alloy. Hereinafter, homogenizationheat treating was performed at 1050° C. for 24 hours, and rapid coolingwas performed.

The alloy, having been cooled after the homogenization heat treating, isrolled downed to the thickness of 1 mm, heat treated at 430° C. for 10hours, so a precipitate was formed.

Meanwhile, regarding the high-entropy alloy having been manufactured asdescribed above, a sheet having a thickness of 1 mm was tensile-tested,and mechanical properties were evaluated, which are illustrated in Table1.

TABLE 1 Tensile Yield strength strength Elongation Division AlloyPrecipitate form (MPa) (MPa) (%) Comparative Co₂₀Cr₂₀Fe₂₀Mn₂₀Ni₂₀ — 620480 40 Example 1 Comparative Fe₂₅Ni₂₅Co₂₅Cr₂₅ — 1000 870 35 Example 2Comparative Fe₂₀Mn₂₀Ni₂₀Co₂₀Cr₂₀ — 760 640 15 Example 3 InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.2)Cu₂₀Si_(0.8) Precipitate (Si) 1300 1050 25 Example1 Inventive Fe₂₀Cr₂₀Ni₂₀Co₂₀Mn₁₈Nb_(2.0) Precipitate (Nb) 1320 1120 20Example 2 Inventive Fe₂₀Cr₂₀Ni₂₀Mn₁₈Cu₂₀Ag_(2.0) Precipitate (Ag) 13901180 22 Example 3 Inventive Fe₂₀Cr_(19.2)Ni₂₀Co₂₀Cu₂₀Ti_(0.8)Precipitate (Ti) 1230 1010 23 Example 4 InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.2)Cu₂₀Mo_(0.8) Precipitate (Mo) 1320 1140 20 Example5 Inventive Fe₂₀Cr₂₀Ni₂₀Co₂₀Mn_(19.2)Ta_(0.8) Precipitate (Ta) 1250 108022 Example 6 Inventive Fe₂₀Cr₂₀Ni₂₀Co₂₀Mn_(19.8)C_(0.2) Carbide (M_(x)C)1330 1190 20 Example 7 Inventive Fe₂₀Cr₂₀Ni₂₀Co₂₀Mn_(19.6)V_(0.2)C_(0.2)Carbide (M_(x)C) 1460 970 30 Example 8 InventiveFe₂₀Cr₂₀Ni₂₀Mn_(19.6)Cu₂₀Ti_(0.2)C_(0.2) Carbide (M_(x)C) 1490 990 28Example 9 Inventive Fe₂₀Cr_(19.8)Ni₂₀Co₂₀Mn₂₀N_(0.2) Nitride (M_(x)N)1410 920 31 Example 10 Inventive Fe₂₀Cr₂₀Ni₂₀Mn_(19.8)Cu₂₀N_(0.2)Nitride (M_(x)N) 1390 925 35 Example 11 InventiveFe₂₀Cr₂₀Ni₂₀Co₂₀Mn_(18.6)N_(0.2)C_(0.2) Carbonitride (M_(x)(C, N)) 1180920 26 Example 12 Inventive Fe₂₀Cr₂₀Ni₂₀Mn_(19.6)Cu₂₀Si_(0.2)B_(0.2)Precipitate (Si) 1350 940 24 Example 13

As illustrated in Table 1, in the case of Inventive Examples 1 through 6satisfying a composition according to the present disclosure and formingvarious alloying precipitates in a matrix, Inventive Examples 7 through12 satisfying the composition and forming a carbide (M_(x)C, M=Ti, Zr,Mo, W, Nb, V, or Ta), a nitride (M_(x)N, M=Ti, Zr, Mo, W, Nb, V, or Ta),a carbonitride (M_(x)C,N, M=Ti, Zr, Mo, W, Nb, V, or Ta), or a boride(MB_(x), M=Ti, Zr, Mo, W, Nb, V, or Ta), and Inventive Example 13satisfying the composition and forming an alloying precipitate by addingan interstitial alloying element B, it is confirmed that excellentstrength and ductility are secured in balance, compared to ComparativeExample. In detail, in the case of Comparative Examples 1 through 3,precipitates are not particularly observed. However, in the case ofInventive Example according to the present disclosure, it is confirmedthat needle-like, spherical, and various shaped precipitates are formedand excellent strength and ductility are secured.

Meanwhile, FIGS. 2A and 2B are images of a microstructure of InventiveExample 7. In FIG. 2A, it is confirmed that coarse Cr carbides areformed in the matrix before secondary heat treatment. In FIG. 2B, it isconfirmed that nanoscale spherical carbides are formed after secondaryheat treating, the spherical carbides block dislocation movement, so analloy may be strengthened.

FIG. 3 is an image of a microstructure of Inventive Example 2. It isconfirmed that a needle-like precipitate formed after secondary heattreatment are uniformly dispersed, the precipitates block dislocationmovement in a matrix, so the matrix may be strengthened.

As set forth above, according to an exemplary embodiment, a matrix, aswell as nanoscale nitride, carbide, or boride precipitates are formed ina high-entropy alloy matrix, so excellent strength and ductility may beimplemented. Therethrough, a high-entropy alloy may be widely used.

While exemplary embodiments have been shown and described above, it willbe apparent to those skilled in the art that modifications andvariations could be made without departing from the scope of the presentinvention as defined by the appended claims.

What is claimed is:
 1. Precipitation hardening high-entropy alloy, thehigh-entropy alloy comprising: four or more elements selected from thegroup consisting of more than 5 wt % to 35 wt % or less of iron (Fe),more than 5 wt % to 35 wt % or less of chromium (Cr), more than 5 wt %to 35 wt % or less of nickel (Ni), more than 5 wt % to 35 wt % or lessof manganese (Mn), more than 5 wt % to 35 wt % or less of cobalt (Co),more than 5 wt % to 35 wt % or less of copper (Cu); one or more elementsof 1) and 2): 1) one or more of 0.01 wt % to 1.5 wt % of C, 0.01 wt % to1.5 wt % of N, and 0.01 at % to 1.5 wt % of B, 2) one or more of 0.01 wt% to 5 wt % of Ti, 0.01 wt % to 3 wt % of Zr, 0.01 wt % to 5 wt % of Hf,0.01 wt % to 5 wt % of Mo, 0.01 wt % to 5 wt % of W, 0.01 wt % to 5 wt %of Nb, 0.01 wt % to 5 wt % of V, 0.01 wt % to 5 wt % of Ta, 0.01 wt % to5 wt % of Ag, 0.01 wt % to 5 wt % of Si, 0.01 wt % to 5 wt % of Cu, and0.01 wt % to 5 wt % of Ge, and inevitable residual impurities; whereinthe high-entropy alloy is provided with a matrix in which precipitatesare dispersed.
 2. The precipitation hardening high-entropy alloy ofclaim 1, wherein the precipitate is one or more of 1) and 2): 1) one ormore of carbides (M_(x)C), nitrides (M_(x)N), carbonitrides (M_(x)C,N),and borides (MBx); and 2) one or more of precipitates that include oneor more of Ti, Zr, Hf, Mo, W, Nb, V, Ta, Ag, Si, Cu, or Ge, andintermetallic compounds thereof.
 3. The precipitation hardeninghigh-entropy alloy of claim 1, wherein the precipitate has the diameterof 0.5 nm to 50 nm, and the spacing between dispersed precipitates is 1nm to 500 nm.
 4. A method of manufacturing a precipitation hardeninghigh-entropy alloy, comprising the following steps: (a) preparingconstituent materials including four or more elements selected from thegroup consisting of more than 5 wt % to 35 wt % or less of Fe, more than5 wt % to 35 wt % or less of Cr, more than 5 wt % to 35 wt % or less ofNi, more than 5 wt % to 35 wt % or less of Mn, more than 5 wt % to 35 wt% or less of Co, and more than 5 wt % to 35 wt % or less of Cu, one ormore elements of 1) and 2): 1) one or more of 0.01 wt % to 1.5 wt % ofC, 0.01 wt % to 1.5 wt % of N, and 0.01 at % to 1.5 wt % of B, 2) one ormore of 0.01 wt % to 5 wt % of Ti, 0.01 wt % to 3 wt % of Zr, 0.01 wt %to 5 wt % of Hf, 0.01 wt % to 5 wt % of Mo, 0.01 wt % to 5 wt % of W,0.01 wt % to 5 wt % of Nb, 0.01 wt % to 5 wt % of V, 0.01 wt % to 5 wt %of Ta, 0.01 wt % to 5 wt % of Ag, 0.01 wt % to 5 wt % of Si, 0.01 wt %to 5 wt % of Cu, and 0.01 wt % to 5 wt % of Ge, and inevitable residualimpurities; (b) manufacturing an alloy by melting the constituentmaterials of step (a), having been prepared, using casting, arc melting,or powder metallurgy; (c) homogenization heat treating the alloy, havingbeen manufactured, at a temperature within a range of 600° C. to 1200°C.; (d) cooling the alloy after the homogenization heat treating; and(e) secondary heat treating the alloy by maintaining the alloy at atemperature within a range of 300° C. to 800° C. for a certain period oftime after cooling step (d) and subsequently cooling the alloy.
 5. Themethod of claim 4, wherein the homogenization heat treating step (c) isperformed for 1 hour to 48 hours.
 6. The method of claim 4, wherein thesecondary heat treating step (e) is performed by maintaining the alloyat for 0.5 hour to 72 hours at temperature and cooling the alloy.
 7. Themethod of claim 4, wherein the secondary heating treating of step (e) isperformed by maintaining the alloy at a temperature within a range of300° C. to 800° C. with a solution treatment above 700° C.